Road grade and vehicle mass are two parameters that affect a number of vehicle control functions. Such functions include powertrain control, energy management control, transmission control, brake control and stability control. For example, conventional vehicles include an internal combustion engine which provides torque for propelling the vehicle. The engine provides torque through the transmission to the drive wheels, even when the engine is idling. Such torque is referred to as creep-torque. When a vehicle is stopped on an inclined surface, this creep-torque supplements torque applied by a brake system (brake torque) to maintain the vehicle in a stationary position. If the engine were to shutdown, while the vehicle was stopped on the incline, the engine creep-torque would be eliminated and additional brake torque would be needed to maintain the vehicle position and prevent the vehicle from rolling backwards. The amount of additional brake torque needed is based on road grade and vehicle mass.
A micro-hybrid vehicle may enable a stop/start strategy for starting and stopping the vehicle engine during a driving event. The engine is shutdown if no power is required (e.g. while waiting at a traffic light). As soon as power is requested, the engine is automatically restarted. By avoiding unnecessary engine idling, the vehicle's fuel economy will be improved. A micro-hybrid having start/stop functionality may adjust brake pressure to maintain a vehicle position when the engine is shutdown while the vehicle is stopped on an incline. Such a micro-hybrid estimates road grade and vehicle mass, and adjusts brake pressure based on these estimates.